Status: OUT
The gap between checking a condition and acting on it is a recurring design concern: the payment system has two independent TOCTOU windows in the same code path, while the notification system defensively re-checks rate limits at both send and process time — demonstrating that temporal check gaps require explicit architectural mitigation rather than assuming atomicity.
Payment shows the bug (unclosed temporal gap), notification shows the fix (double-check pattern) — together establishing temporal gaps as a first-class design concern
Depends on (SL): payment-toctou-double-jeopardy, notification-defensive-double-rate-check